Method of preventing the decomposition of carbon tetrachloride and product thereof



Patented May 10, 1932 UNETED STATES rara'r FFEQE LAWRENCE F. MARTIN ANDARTHUR A. ELSTQN, OF MIDLAND, MICHIGAN, ASSIGNORS TO THE DOW CHEMICALCOMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN METHOD OFPREVENTING THE DECOMPOSITION OF CARBON TETRQACHLORIDE' AND PRODUCTTHEREOF No Drawing. Application filed May 3, 1929, Serial No. 360,310.Renewed March 7, 1931.

which, when present in only relatively small amount, have the propertyof inhibiting such decomposition. More particularly, it is concernedwith the preservation of chlorinated or brdminated derivatives of thesaturated or unsaturated aliphatic series of hydrocarbons which have atendency to decompose under the influence of air, moisture, heat orlight, or a combination of such factors, with the consequent formationof corrosive chloroor bromo-compounds. Examples of such halogenatedhydrocarbons are carbon tetrachloride, CCh, chloroform, CHCltrichlorethylene, 0 1101 tetrachlorethylene, C2Cl and the like.

A source of trouble connected with the use of the aforementionedhalogenated hydrocarbons is the corrosion of metal surfaces exposedthereto, either in the liquid, gaseous or combined phases, andespecially in the presence of water. The problem may be subdivided intotwo principal factors, (1) corrosion of metal containers with which theliquid comes in contact and (2) deterioration of the fluid itself, dueto the presence of decomposition products. Of the aforementioned factorsinfluencing the decomposition of halogenated aliphatic hydrocarbons, i.e., air, moisture, light and heat, moisture plays the greatest part inthe present problem, the others being of lesser importance. If water isabsent, the corrosion of metallic surfaces produced as a result of theaction of the decomposition products of the halogenated hydrocarbon, e.g. carbon tetrachloride, is negligible.

It is known that certain compounds, such as benzaldehyde, tend toprevent corrosion of metals by carbon tetrachloride, as shown byFerguson in U. S. Patent 1,151,255, thus making the carbon tetrachloridemore suitable for use in metallic fire-extinguisher containers. We havenow discovered that in the presence of considerable moisturedecomposition of carbon tetrachloride or like halogenated aliphatichydrocarbon may be in hibited, or, at least, largely prevented by theaddition thereto of a hydrogenated aromatic hydrocarbon, such acyclohexane. It is known that cyclohexane forms an azeotropic mixturewith carbon tetrachloride, hence the former is carried alon with thelatter when the mixture is subjected to distillation. Such formation ofa constant boiling mixture is particularly advantageous in the presentcase because no material separation of the effective inhibitory agentoccurs when the mixture is distilled for the purpose of purificationafter use, e. g. in dry-cleaning. Furthermore, the protective orpreservative effect is exerted in the vapor phase to an equal degree asin the liquid phase. To the accomplishment of the foregoing and relatedends, the invention, then, consists of the steps and new productshereinafter fully described and particularly pointed out in the claims,the following description setting forth but several of the various waysin which the principle of the invention may be employed.

Of various preservative compounds that We have tested, we have foundcyclohexane to be the mosteffective in reducing the decomposition ofcarbon tetrachloride in the presence of moisture. The following detailedexamples will serve to demonstrate the beneficial effect of theadmixture of the former with the latter compounds forreducing thecorrosion of metals exposed to the action of the mixture when water ispresent.

Ewample In a set of comparative tests, strips of lead and nickel ofknown weight were suspended above the surface of the liquid boilingunder reflux for a period of ten days, the metal surfaces being exposedto the vapors and restrips, as shown in the following table Loss inweight, grams (100 cm!) day Metal 0, C1 1 C H oo14+1o% H20 (81-0 1 6: @3

Nickel o. 0057 o. 0013 Lead o. 0157 o. 0011 Inspection of the abovetable shows conclusively that the presence of cyclohexane has the eifectof greatly reducing the corrosion of the metallic samples under theconditions of the tests. It, therefore, becomes apparent thatdecomposition of the carbon tetrachloride due to the action of water-hasbeen repressed or prevented to a corresponding degree by the additionthereto of a minor proportion of cyclohexane. Thereby a simple means isafforded of limiting or preventing the deleterious action of water uponcarbon tetrachloride.

The present method has not only the advanta es of ease of applicationand cheapness ailong with attainment of preservative results, but theuse for the purpose in question of a material forming an azeotropicsolution with carbon tetrachloride is especially desirable because suchmaterial is not separated from the mixture in case repurificationthereof by distillation becomes necessary. Regardless of suchcontingency the two components of the mixture are maintained at alltimes in approximately their original proportions.

We have found that the extent to which the decomposition of carbontetrachloride is repressed or inhibited varies somewhat with the amountof preservative added. HOW- ever, when the cyclohexane is present infrom five to forty per cent by volume of the mixture, the decompositionis inhibited sufficiently for practical use. Although cyclohexane byitself is inflammable, the above mixture is non-inflammable, and isoutside of the limits within which combustion can be spontaneouslymaintained.

Other modes of applying the principle of our invention may be employedinstead of the one explained, change being made as regards the methodherein disclosed, provided the step or steps stated by any of thefollowing claims or the equivalent of such stated step or steps beemployed.

We therefore particularly point out and distinctly claim as ourinvention corresponding to from five to forty per cent by volume of theresultant mixture.

5. 'As a composition of matter, a halogenated aliphatic hydrocarbonhaving dissolved therein cyclohexane.

6. As a composition of matter, a halo enated aliphatic hydrocarbonhaving disso ved therein cyclohexane in amount from five to forty percent by volume of the resultantmixture.

7. As a composition of matter, carbon tetrachloride having dissolvedtherein cyclohexane.

8. As a composition of matter, carbon tetw rachloride having dissolvedtherein cyclohexane in amount from five to forty percent by volume ofthe resultant mixture.

9. Themethod of preventing the decomposition of a chlorinated methanewhich com-,

prises adding thereto cyclohexane.

10. As a composition of matter, a. chlori-;v nated methane havingdissolved therein cyv clohexane.

11. As a composition of matter, chloroform having dissolved thereincyclohexane. Signed by us this 27 day of April, 1929.

LAXVRENOE F. MARTIN. I ARTHUR A. ELSTON.

